Multiple radio base station networks have been developed to overcome a variety of problems with single radio base station networks such as spanning physical radio wave penetration barriers, wasted transmission power by portable computing devices, etc. However, multiple radio base station networks have their own inherent problems. For example, in a multiple base station network employing a single shared channel, each base station transmission is prone to collision with neighboring base station transmissions in the overlapping coverage areas between the base stations. Therefore, it often proves undesirable for each base station to use a single or common communication channel.
In contradistinction, to facilitate the roaming of portable or mobile devices from one coverage area to another, use of a common communication channel for all of the base stations is convenient. A roaming device may easily move between coverage areas without loss of connectivity to the network.
Such exemplary competing commonality factors have resulted in tradeoff decisions in network design. These factors become even more significant when implementing a frequency hopping spread spectrum network. Frequency hopping is a desirable transmission technique because of its ability to combat frequency selective fading, avoid narrowband interference, and provide multiple communications channels.
Again, however, changing operating parameters between coverage areas creates difficulties for the roaming devices which move therebetween. In particular, when different communication parameters are used, a portable or mobile device roaming into a new base station coverage area is not able to communicate with the new base station without obtaining and synchronizing to the new parameters. This causes communication backlog in the network.
Computer terminals and peripheral devices are widely used. Many types of computer terminals exist which vary greatly in terms of function, power and speed. Many different types of peripheral devices also exist, such as printers, modems, graphics scanners, text scanners, code readers, magnetic card readers, external monitors, voice command interfaces, external storage devices, and so on.
To communicate with such peripheral devices, portable computers have been adapted to use RF (Radio Frequency) and infrared communication. Such configurations, however, do not always provide for efficient communication. For example, a portable computer device may be mounted in a delivery truck and a driver may desire to transmit data to, or receive data from, a host computer or peripheral device at a remote warehouse location. While permitting such transmissions, wide area networks (WANs) only provide point-to-point communications, use a narrow bandwidth, and often exhibit heavy communication traffic. Moreover, WANs require relatively higher transmission power—a negative factor in the ever increasing need for power savings associated with portable transceiving devices. As a result, WANs are generally slow and expensive, and simply do not provide an effective overall solution.
The need for portable, or otherwise mobile, devices has led to smaller, lower power designs. Portable computer terminals have achieved such size and power reductions by decreasing local processing and storage resources. In contrast, application programs are growing in size and functionality, requiring more and more processing and storage resources to operate. As a result, portable computer terminals have been effectively disabled from independently performing many needed tasks. Others have been stretched to a nearly unacceptable limit of portability, battery life and processing and storage ability.
To address such needed tasks, remote processing and storage techniques are currently being used. For example, stationary remote host computers having superior processing and storage capability are often connected via a WAN network to a mobile computer terminal. In such configurations, whenever the mobile terminal desires access to data, it sends a request across the WAN for such data. Similarly, when it desires remote processing, the mobile computer terminal formulates a request which is sent to the host computer over the WAN. However, the mobile terminal is still required to use the relatively expensive and delayed services provided by the WAN for each such request, which often prove unacceptable for a given task.
Similarly, the relaying of communications through even lower power radio networks is required in many multi-hop radio environments. Repetitive requests and associated delivery of data, program or processing resources from a source (e.g., a mobile computer terminal) to a destination (e.g., a host computer) takes its toll on overall network performance.
Thus, there is a need for a wireless communication network that provides efficient distribution and utilization of network resources in support of portable and otherwise mobile computer devices.
Yet another object of the invention is to provide a method and apparatus wherein collisions are minimized in overlapping coverage areas by utilizing uncommon communication channel characteristics in a multiple base station network, while still providing seamless communication for roaming devices by informing roaming devices of the nature of the neighboring base station communication channel characteristics.
A still further object of the present invention is to provide a hierarchical communications system for providing an efficient communication pathway for data and programming objects.
Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.